The present invention relates to messenger ribonucleic acids (mRNAs) comprising 4′-thio-modified nucleotide residues, compositions comprising those mRNAs, and methods of making and using same.
Gene therapy using messenger RNA has been proposed as an approach for the treatment of a variety of diseases. The concept of introduction of messenger RNA (mRNA) as a means of protein production within a host has been reported previously. Yamamoto, A. et al. Eur. J. Pharm. 71:484-489 (2009); Debus, H. et al. J. Control Rel. 148:334-343 (2010). However, successful administration of mRNA for in vivo protein production typically required mRNA being packaged (such as, e.g., mRNA complexed with a polymer or lipid carrier). See, e.g., International Patent Appl. Publ. Nos. WO 2011/06810 and WO 2012/170930. Administration of unpackaged (naked) mRNA required chemically-modified nucleotides to be incorporated within an mRNA to result in a more stable and beneficial therapeutic. See, e.g., M. Kormann et al. Nature Biotech. 29:154-159 (2011); K. Kariko, Molecular Therapy 16(11):1833-1840 (2008).
The administration of mRNAs encoding a therapeutic protein that can be produced in vivo may provide significant advantages over administration of DNA encoding the therapeutic protein as well as direct administration of the therapeutic protein. However, while the development of therapeutic mRNAs encoding therapeutic proteins represents a promising advancement in medical therapies, the utility of such treatments can still be limited by the poor stability of mRNAs in vivo, particularly those encoding full length proteins.
In particular, poor stability of mRNAs used in gene replacement therapy can result in insufficient or less optimal production of the encoded therapeutic protein in vivo. Following the administration of an mRNA that encodes a therapeutic protein, the mRNA may undergo degradation, for example upon exposure to one or more nucleases in vivo. Ribonucleases (e.g., endoribonucleases and exoribonucleases) represent a class of nuclease enzymes that are capable of catalyzing the degradation of RNA into smaller components and thereby render the mRNA unable to produce the therapeutic protein. Nuclease enzymes (e.g., RNase) are therefore capable of shortening the circulatory half-life of, for example, synthetically or recombinantly-prepared mRNAs. Following nucleolytic degradation, an mRNA is not translated, and thus, is prevented from exerting an intended therapeutic benefit, which can significantly reduce the efficacy of the mRNA gene therapy.